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extraction. An advantage of the water and resin method is that the microstructure of the soil is not substantially changed when using these methods. An intensity measurement was not in itself sufficient for analysis of the phosphorus status, since the intensity drops rapidly when soil releases phosphorus.

A prerequisite for efficient ammonia removal in air stripping is that the pH of the liquid to be stripped is sufficiently high. Swine manure pH is usually around 7. At pH 7 (at 20°C), only 0.4% of ammonium is in ammonia form, and it is necessary to raise the pH of swine slurry to achieve efficient ammonia removal. Because manure has a very high buffering capacity, large amounts of chemicals are needed to change the slurry pH. The present study showed that efficient air stripping of manure can be achieved with a small amount of chemicals and without strong bases like NaOH. Slurry was subjected to aerobic biological treatment to raise pH before stripping. This facilitated 8 to 32% ammonia removal without chemical treatment. The slurry was further subjected to repeated cycles of stripping with MgO and Ca(OH)2 additions after the first and second strippings, respectively, to raise slurry pH in between the stripping cycles. After three consecutive stripping cycles, 59 to 86% of the original ammonium had been removed. It was shown that the reduction in buffer capacity of the slurry was due to ammonia and carbonate removal during the stripping cycles.

Abstract. The effect on soil porosity of tractor compaction of soil in the spring was studied by taking cylindrical core soil samples. The

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Runoff from clayey soils often contains abundant particulate phoshorus (PP), part of which may solubilize in surface waters. Monitoring losses of potentially bioavailable forms of PP is expensive, calling for other ways to predict them. Such predictions could be based on soil loss and available soil P indices, e.g., agronomic P status. To study correlations between P pools in runoff versus soil P saturation (by Mehlich 3 extraction; DPSM3) and acetate soil test P (PAc), 15 clayey soils of south Finland were subjected to laboratory rainfall simulation. Runoff from these simulations was analyzed for concentrations of suspended soil (TSS), dissolved molybdate-reactive P (DRP), total P (TP), and, as normalized to soil loss, potentially bioavailable forms of PP: desorbable (anion exchange resin-extractable, AER-PP/TSS) and redox-labile PP (bicarbonate- dithionite-extractable, BD-PP/TSS). Correlation coefficients (r2) between DPSM3 and DRP, AER-PP/ TSS, and BD-PP/TSS equaled 0.92, 0.77, and 0.45, respectively. Runoff P forms were also correlated to soil PAc with r2 values of 0.84, 0.56, and 0.58 for DRP, AER-PP/TSS, and BD-PP/TSS, respectively. Prediction of soil loss-normalized concentrations of potentially bioavailable PP by the agronomic PAc test was considered possible. However, such predictions have a high degree of uncertainty, evidenced by comparison to published field data. Acceptably accurate predictive equations would require a large material as a basis for their construction, and soils should probably also be grouped according to other soil properties that would account for variation in P sorption capacity.;

The placement of fertilizer was studied in the field trial on a clay soil in Southern Finland. The placement of fertilizer in the depth of 8 cm gave 28 per cent greater grain yield of spring wheat, and the placement in the depth of 12 cm 26 per cent greater grain yield than the surface dressing. The growth of shoots on the soil receiving placement was much better than on the soil receiving surface dressing. The results of shoot analyses showed that the placement caused a much greater uptake of nutrients than the surface dressing. The uptake of nitrogen was relatively most increased by the placement, somewhat less that of potassium and least that of phosphorus. The ripening of wheat was speeded up by the placement, which probably was due to the better early uptake of nitrogen and to the better uptake of phosphorus by means of the placing. The superiority of the placement to the surface dressing could be explained by the distribution of nutrients in the experimental soil during the dry early part of the growth season. A great deal of fertilizer nitrogen, phosphorus and potassium remained near the surface of the soil receiving surface dressing, and plants were not able to take up nutrients from the dry surface layer. On the contrary, the placed nutrients were deeper, in moister soil and better within the reach of wheat roots. Any movement of ammonium nitrogen was not found by the used methods. Nitrate nitrogen appeared to move to a greater extent particularly in the irrigated plots.

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